This application is a 371 of PCT/EP99/08507 filed Nov. 19, 1999.
The present invention relates to prolactin lowering drugs.
Extracts from Vitex agnus-castus (agnus castus, chaste tree) have been used for long in the medicine of natural remedies for treatment of the premenstrual syndrome. Shortly prior to menstruation, patients frequently complain of tenseness in the breasts, clinically accompanied by an elevated prolactin content.
Extracts from Vitex agnus-castus possess prolactin lowering properties which could furthermore be ascertained clinically and pharmacologically in the prior art. Attempts have been numerous in the prior art to characterize or even isolate those substances in Vitex agnus-castus that are responsible for an alleviation of the premenstrual sydrome.
Thus the dissertation by Daniel Berger entitled, xe2x80x9cVitex agnus-castus: Unbedenklichkeit und Wirksamkeit beim prxc3xa4menstruellen Syndrom, Wirkprinzipien and Wirkmechanismen eines neu entwickelten Extraktesxe2x80x9d [Vitex agnus-castus: Recognized safety und effectivity in the premenstrual syndrome, effective principles and mechanisms of a newly developed extract] at the Faculty of Philosophy and Natural Science of Basle University, of Jan. 13, 1998 deals with a multiplicity of aspects brought into connection with Vitex agnusastus.
This dissertation describes a number of different constituents which were taken into consideration for an explanation of the pharmacological properties of the drug.
Thus in Vitex agnus-castus the iridoid glycosides aucubin, agnuside and eurostoside are found both in the leaf drug and in the fruit drug.
Moreover the lipophilic flavonols casticin, penduletin, chrysosplenol D and the 3,6,7,4xe2x80x2-tetramethyl ether of 6-hydroxykaempferol could be isolated from the fruit.
The prior art furthermore describes that progesterone, 17xcex1-hydroxy-progesterone, testosterone and epitestosterone could be detected in the fruit of Vitex agnus-castus.
Apart from this, a total of about 73 different compounds can be found in the fruit of Vitex agnus-castus, above all monoterpenes such as xcex1-pinene, sabinene, xcex2-phellandrene and 4-terpineol, and sesquiterpenes such as xcex2-caryophyllene, allo-aromadendrene, germacrene B, spathulenol and xcfx84-cadinol.
Besides the classes of substances already mentioned above, considerable amounts of fatty -acids can moreover be found in the fruit of Vitex agnus-castus, as there are saturated, monounsaturated and polyunsaturated fatty acids. Thus, e.g., xcex1-linolenic acid, oleic acid, stearic acid, palmitic acid, linoleic acid and adrenic acid were detected in the fruit.
Further examination of the essential oil from the fruit of Vitex agnus-castus also uncovered the presence of diterpenes. The above mentioned dissertation provides information that the following diterpenes were isolated from the fruit of Vitex agnus-castus:
rotundifuran, vitexilactone and 6xcex2,7xcex2-diacetoxy-13-hydroxy-labda-8,14-diene, the structural formulae of which are represented hereinbelow: 
In this prior art a multiplicity of testing processes were performed in order to find out about the effective mechanisms of extracts from Vitex agnus-castus, and whether a particular substance or a particular class of substances is suited for explaining the pharmacological effects of the full extract.
Thus, e.g., measurements were carried out on the various opioid receptors, on the benzodiazepin receptor, on the serotonin reuptake site, on the histamine-H1 receptor and on the dopamine-D2 receptor.
In order to verify the results of the receptor binding studies on the dopamine-D2 receptor with fractions from Vitex agnus-castus and thereby find the actual active substances, experimentation was carried out in the above described prior art with the known constituents of Vitex agnus-castus (pure substances). These pure constituents were aucubin, casticin, homoorientin, linoleic acid, luteolin-7-glycoside, orientin and the diterpenes vitexin, rotundifuran, 6xcex2,7xcex2-diacetoxy-13-hydroxy-labda-8,14-diene.
The dissertation does, however, explicitly state on page 154 in Chapter 2.3.4.5 that none of the tested substances had a sufficiently low IC50 value for being able to exaplain, as a single substance, the activity and thus the pharmacological effects of the full extract or of a lipophilic hexane fraction from Vitex agnus-castus.
Starting out from this prior art, it was an object of the present invention to provide pure substances from the fruit of Vitex agnus-castus, whereby a drug for treating the premenstrual syndrome may be produced in pharmaceutical formulation.
This object is attained by a drug in accordance with claim 1 and by the novel substances in accordance with claim 12 and claim 14.
In the framework of the present invention it was surprisingly found that compounds from the class of bicyclic diterpenes have a prolactin lowering effect on cultivated pituitary cells from rats. It is highly likely that this mechanism can be transferred to humans.
Herein the effective diterpenes may have a skeletal structure both of the labdane type and of the clerodane type: 
In particular it was found that a prolactin lowering effect on cultivated pituitary cells may be achieved with compounds in accordance with the following general formulae I to IV with, at the same time, low cytotoxicity: 
with R1=H, C1 to C3 alkyl or C1 to C3 acyl;
wherein the rings A and/or B in the case of general formulae (I) or (II) are optionally substituted in position 1, 2, 3, 4, 6, 7, 8 or 9 with at least one OX radical, with X=H, C1 to C3 alkyl or C1 to C3 acyl;
wherein the rings A and/or B in the case of general formulae (III) or (IV) are optionally substituted in position 1, 2, 3, 4, 6, 7, or 8 with at least one OX radical, with X=H, C1 to C3 alkyl or C1 to C3 acyl;
wherein optionally at least one carbon atom in positions 17, 18, 19 and 20 is substituted with an OX radical, with X=H, C1 to C3 alkyl or C1 to C3 acyl;
wherein optionally at least one CH3 group in positions 17, 18, 19 and 20 is replaced by a COOH group;
wherein optionally at least one of ring positions 1, 2, 3, 6, or 7 is a keto group; and
wherein optionally at least one double bond is present in ring positions 1, 2, 3, 6, 7, 8, 8(17) of formulae (I) and (Ill); and
wherein optionally at least one double bond is present in ring positions 1, 2, 3, 4(18), 6, 7, 8, 8(17) of formulae (II) and (IV).
Moreover the following compounds are preferred embodiments of the present invention: 
as well as
cleroda-Y,14-dien-13-ol, with Y=ring position 1, 2, 3, 4(18), 6, 7 or 8(17); and
cleroda-Y,Z,14-trien-13-ol, with Y or Z=ring position 1, 3, or 1, 4(18) or 1, 6 or 1, 7 or 1, 8(17) or ring position 2,4(18) or 2, 6 or 2, 7 or 2, 8(17) or ring position 4(18), 6 or 4(18), 7 or 4(18), 8(17) or ring position 6, 8(17).
It was possible to enrich and characterize the like compounds from an ethanolic-aqueous extract from fruit of Vitex agnus-castus by fractionated lipophilic extraction, and to determine their structures.
In particular extraction with highly lipophilic solvents such as medium-length chain hydrocarbons C5-C10, in particular with n-hexane, resulted in strong enrichment of the prolactin lowering effect. Moreover extraction from fruit of Vitex agnus-castus with supercritical carbon dioxide allowed for strong enrichment of the effective principle, which could be reduced to the compounds in accordance with general formulae I to IV.
All of the compounds in accordance with the invention, the structural formulae of which are represented above, exhibit inhibition of the released prolactin on lactotropic cells from rats"" pituitary glands.
In separate studies on cytotoxicity it was found that all of the compounds isolated and characterized in accordance with the invention exhibited low cytotoxicity, a fact that renders them particularly attractive in terms of pharmaceutical formulation.
It was furthermore found that the named substances also bind to the human recombinant dopamine-D2 receptor.